In the forthcoming grant period we propose: (1) To continue our studies of the development of the avian visual system, taking advantage of the manipulability of certain parts of this system in chick embryos to determine such developmental features as the control of cell proliferation and the establishment of axial polarity in the optic tectum, the capacity of the system for regeneration and plasticity, and the ontogenetic origin of the central noradrenergic system. (2) To explore further the response of the mammalian cerebral cortex to early sensory deprivation using the distinctive barrel-like cell formations inlamina IV of the mouse somatosensory cortex which, because of their limited size and ready-identifiability, lend themselves more effectively to experimental and morphological analysis than most cortical structures. (3) To extend the capabilities of the computer-system developed in our laboratory, for the quantitative analysis of neuroanatomical data. And (4) to maintain, and to continue to make available, this system to others in the visual sciences community who wish to use it, or to adapt the programs we have developed for their own purposes.